Today Network and Service Providers are aware of the increasing data traffic volumes and as such they are strategically moving investigations toward a single integrated voice and data infrastructure. In this context IP is gaining the role of the integration layer for multiple services. Nevetheless incumbent NSPs that build a multi-service IP network are going to need connectivity to its preexisting legacy networks (e.g. ATM. SONET, SDH). This reason motivates the introduction of a client-independent Optical Transport Network (OTN) as a missing link to guarantee a smooth evolution from legacy networks to a data-centric OTN. The scope of this paper is to give some guidelines about the definition of functionality and architectures of a multilayers infrastructure supporting the transport of data and circuit-based services. Particularly, the identification of the different service requirements, as well as the understanding of the allowed degradation, provide a picture of the needed survivability mechanism of IP over OTN scenarios
